Safety legislation in many western jurisdictions requires that PTO shafts and their connecting members are covered by a guard which reduces the risk of injury for the operator. Guards fitted to the PTO shafts of agricultural equipment are typically formed of a plastic material and comprise a tube with enlarged end portions to accommodate the coupling mechanism. A short length of chain is usually employed to attach the guard to a fixed structure which prevents rotation. To minimize wear of the plastic guard, a guard bearing is often fitted to the PTO shaft to allow the shaft and guard to rotate with respect to one another. Furthermore, to prevent axial movement of the guard relative to the shaft, a means of securing the guard to the bearing member or shaft is often provided in the form of a releasable clip.
United Kingdom patent application GB-2,427,009 discloses a safety guard for a PTO with a releasable locking mechanism which comprises a pair of pivoting levers which releaseably engage a groove on a guard bearing mounted to the PTO shaft. Each lever is manually operated between a locked and an unlocked position.